Tire Pressure

[tojo7089]

Question about what psi I should be running. I have a 2006 Dodge Ram 1/2 ton. The OEM tires are 245/70-17. I bought the truck with 265/70-17 on it, so that's what I've been running it with. The door jam says 35 psi but that's with OEM tires. I just bought new tires and the max tire pressure is 51 psi. I usually like to go about 10% above what the door jam says, but just wondering about running larger tires and if that makes a difference?

 

[CR94]

You could safely run a little lower pressure with the larger tires, but don't have to do so. Suit yourself.

 

[BMWTurboDzl]

Have you check your owners manual? Sometimes the list recommended PSI for other sizes.

 

[maxdustington]

I go between the door and what is says on the tire. That's about 36 PSI on a P225R16 or whatever. Don't know my tire size. If you use your truck to haul things in the bed, put a couple more PSI in the rears.

 

[tojo7089]

I have checked the owner's manual and it just references the door jam information. I'm mainly doing it for optimum tire wear. My previous tires were Cooper Discoverer AT/3. I had good luck with them previously but this last set only lasted about 20,000 miles. I'm pretty sure it was my fault. I saw the "max tire pressure" of 44 psi on the tire and that's what I ran them at. Also, after getting the new tires on, the next morning I checked them and they were at 32. Did the installer really fill them only to 32 psi????? Why?

 

[xBa380]

Tire performance is more important than tire wear. Too high of pressure hurts ride quality and reduces traction, cornering, tire wear, etc… Note, going up or down a few PSI from door jam is fine for getting the "feel" you want, but I can't imagine running at the max pressure of the sidewall… Tire pressure is dictated by the manufacturer by design... There is a reason for it. If the manufacturer calls out 32psi, run around that pressure. Just because a tire is rated for up to 51psi in many cases, you won't want to run the tire at that.

 

[carviewsonic]

I would go with the door jamb 35 psi for general running around and highway use. If heavily loaded or towing I would raise the rear tire pressure to 40 psi. I run my (usually) lightly loaded work truck on mostly gravel roads, and found that the tires last a lot longer running them 5 psi less than the door jamb. Edit to say: I'm talking 1/2 ton pickups, not 3/4 ton.

 

[BrocLuno]

I run what makes an even tread wear pattern. Drive in on pavement until the tread is nice and black and then run it on a smooth gravel road a 100 feet or so. Look at the contact pattern on the edges. If too much round shoulder is still black you are too high. If the edges show gray, you are too low. Door stick PSI is for safe handling, including braking. It's a balance. Hard tires will not stop as effectively as "properly" inflated ones. OTOH, soft tires will not carry a load worth a darn. Tire pressure is an adjustable thing. Adjust it so it works right ...

 

[CourierDriver]

Originally Posted by maxdustington

I go between the door and what is says on the tire. That's about 36 PSI on a P225R16 or whatever. Don't know my tire size. If you use your truck to haul things in the bed, put a couple more PSI in the rears.

 

[k1xv]

Max tire pressure should only be used when the weight of the vehicle and cargo are up to the GVWR. At normal loads, you should use the manufacturer recommended pressure for normal tire size, and if you are running a tire that is a bit oversize, you can lower that by a pound or two, but it isn't mandatory.

 

[JLTD]

Originally Posted by tojo7089

I have checked the owner's manual and it just references the door jam information. I'm mainly doing it for optimum tire wear. My previous tires were Cooper Discoverer AT/3. I had good luck with them previously but this last set only lasted about 20,000 miles. I'm pretty sure it was my fault. I saw the "max tire pressure" of 44 psi on the tire and that's what I ran them at. Also, after getting the new tires on, the next morning I checked them and they were at 32. Did the installer really fill them only to 32 psi????? Why?

Optimum tire wear is even wear. To do that you need a pressure that maximizes the contact patch evenly across the entire width of the tire. Reading owner's manuals has shown me that pressure needs to be varied depending on load - for instance when carrying a heavy load or towing, you will likely need somewhere near maximum pressure of the tire. Daily drivers unloaded require less pressure. When I had my F150, max psi was 51 and I used that while towing, it would squirm at 40 where I had it while unloaded. 42 front and 40 rear is where I had things, very even wear across the entire tire. I have found that the placarded psi ends up wearing the outsides of the tires, and that a few more psi evens out the wear. I am currently running 42 psi (on a max 44psi tire) on the 4Runner. I got it used and at 32psi the outsides were worn. Since putting on 10k miles the wear has evened out so probably slightly overinflated right now for the weight...so will let it dial itself back to 40 as the temperatures cool. Edit: yes your tire guy probably set it at 32....seen the same in many tire shops - and have been told it is for liability; basically if they set it to the placarded psi they are covered.

 

[jadatis]

You can most likely do with even 25 psi, if its only for not overheating the tires if you drive max speed of car. The 51 psi is max allowed cold pressure by the tiremaker, 35 psi is the pressure in american system for standard load tires, for wich the maxload of tire is calculated, for speed 99mh/160kmu. I once got hold of the European official formula to calculate pressure for load and speed on tire, and went running with it, America uses this formula since 2006 too. So if you can produce weights on tires( thw most tricky part in it all) and maxspeed used ( and wont go over for even a minute), then I will google the tires for maxload AT 35 or 36 psi , and calculate the needed pressure with some reserve. If you then fill higher its only for fuel saving and roadhandling. But because of the larger tires ( even with OEM) , with relatively high maxload, I expect about 25 psi

 

[Excel]

38-40 wears best IMO for what you are running

 

[CapriRacer]

Allow me to explain about max pressure. The max pressure listed on the sidewall of tires should not be used for any purpose other then what it says - Max usage pressure. Do NOT refer to it when selecting usage pressure (except to say, don't exceed it). That's because tires behave basically the same way regardless of what the max pressure is imprinted on the sidewall - thusly: For a given set of physical dimensions (size), the load carrying capacity vs inflation pressure is the same. You can see this in the load tables. Yes, you will find SLIGHTLY different load tables for the same size, but that is because of a) differences between metric and English units, and b) different theories as to how tires work. Note: Tires work the same, but the formulae that are used to describe this behavior is SLIGHTLY different. So Standard Load passenger car tires will always have a max pressure of 35, 44 or 51 psi, (41 or 50 psi for Extra Load), with the one exception being 36 psi for metric units. HOWEVER, regardless of the max pressure, the load table is the same. I go into much more detail here: http://www.barrystiretech.com/loadtables.html Tire wear vs inflation pressure: First, tire wear is relatively insensitive to inflation pressure. Within a few psi of any value, the wear will be about the same. Further, there are things that impact tire wear that have a greater effect. The most obvious is alignment - BUT - Steering tires tend to wear in the shoulders, while drive tires tend to wear in the center. This is very apparent in RWD cars, where the fronts and rears do different things. FWD cars, where the front tires do both, tend to wear evenly, but if they don't, it's because of alignment and/or the way the car is used (country driving vs city driving)

 

[Rmay635703]

A tires load carrying capacity is achieved at the MaX PSI listed on the sidewall. If you carry a lot of weight that nears the load capacity of the tire make sure you air up unless you like blowouts. If you run around empty you just follow the door placard, but best economy is rarely at the stock PSI Good Luck

 

[JohnnyJohnson]

Originally Posted by Rmay635703

A tires load carrying capacity is achieved at the MaX PSI listed on the sidewall. If you carry a lot of weight that nears the load capacity of the tire make sure you air up unless you like blowouts. If you run around empty you just follow the door placard, but best economy is rarely at the stock PSI Good Luck

Yes I run 6 PSI over the door sticker and it gains me roughly 2 MPG in town and 4 MPG on the freeway. Where the thin oil they claim gains you gives me nothing ever.

 

[JLTD]

Originally Posted by CapriRacer

... First, tire wear is relatively insensitive to inflation pressure. Within a few psi of any value, the wear will be about the same.

Huh?? With all due respect you are dead wrong here. Chronically underinflated tires WILL wear both outside edges. Chronically overinflated tires will wear the center.

 

[CapriRacer]

Originally Posted by Rmay635703

A tires load carrying capacity is achieved at the MaX PSI listed on the sidewall. ……..

Ah …… Mmmm ….. not exactly. Even 44 psi max and 51 psi max passenger car tires achieve their max load carrying capacity at 35 psi.

 

[CapriRacer]

Originally Posted by JLTD

Originally Posted by CapriRacer

... First, tire wear is relatively insensitive to inflation pressure. Within a few psi of any value, the wear will be about the same.

Huh?? With all due respect you are dead wrong here. Chronically underinflated tires WILL wear both outside edges. Chronically overinflated tires will wear the center.

Sorry, but I spent 15 years in tire research and 15 years in field testing of tires. One of the things looked at was trying to get tires to be insensitive to irregular wear. I think where we disagree is over 2 items: 1) How much affect does steering vs drive position have on wear. It's a lot more than you might think. 2) How much pressure is "chronic"? If you are talking 15 psi, then I'll cut you some slack. But that's the kind of level I documented for steer vs drive. Let me give you another example. On many FWD cars, the specified inflation pressure is the same front to rear, in spite of the fact that there is a HUGE weight difference front to rear - yet, there isn't a huge problem with the center wearing on the rear tires (one in proportion to the amount of overinflation.) That's what I mean by insensitive. And in all fairness, the rear tires of a FWD tend to develop irregular wear (some incorrectly call this cupping wear.), but it is driven mostly by alignment - toe, in particular - with inflation pressure aggravating the situation, not being the driver.

 

[JLTD]

Originally Posted by CapriRacer

Originally Posted by Rmay635703

A tires load carrying capacity is achieved at the MaX PSI listed on the sidewall. ……..

Ah …… Mmmm ….. not exactly. Even 44 psi max and 51 psi max passenger car tires achieve their max load carrying capacity at 35 psi.

Structurally for the tire perhaps; however from a lot of reading - and experience- the trailer sway is dangerous at lower pressures.